Method of folding plastic containers



July 27, 1965 c. E. PALMER ETAL I 7 METHOD OF FOLDING PLASTIC CONTAINERSFiled NOV. 8, 1965 3 Sheets-Sheet 1 H67 A4 /Z /4 INVENTORS CHARLES E.PALMER JOSEPH s. LEMANSKI ATTORNEY y 27, 1955 c. E. PALMER ETAL3,196,759

METHOD OF FOLDING PLASTIC CONTAINERS Filed Nov. 8, 1963 FIGS 3Sheets-Sheet 2 Ail - INVENTORS CHARLES E. PALMER JOSEPH S. LEMANSKIATTORN EY y 1965 c. E. PALMER ETAL 3, ,7

METHOD OF FOLDING PLASTIC CONTAINERS 3 Sheets-Sheet 3 Filed Nov. 8, 1963FIG. l2-

INVENTORS CHARLES United States Patent 3,196,759 METHGD 6F FGLDINGPLASTIC CQNTAENERS Charles E. Palmer, Turnpike Road, Somers, Conn, and

.l' oseph S. Lemanshi, Longrneadow, Mass; said Lemanslri assignor tosaid Palmer Filed Nov. 8, 1963, Ser. No. 323,540 11 Claims. (Cl. 93-36)This application i a continuation-in-part of our copending applicationSerial Number 210,639, filed July 18, 1962, Method of Folding PlasticContainers, now abandoned.

The present invention relates to containers, and more particularly tocontainers cold-folded from plastic sheet material and to the blankstherefore and the method of folding the blanks into the containers.

In United States Patent No. 2,954,725, granted to Charles E. Palmer,there is disclosed a novel method and apparatu for cold-foldingsynthetic plastic sheet material having the characteristics ofsemi-rigidity and ability to take and retain a fold such as biaxiallyoriented polystyrene. In cold-folding such plastic sheet material, itgenerally is necessary to fold the plastic sheet material beyond 90degrees in order to obtain the desired permanent set of the fold, and iti also necessary to employ locks which will resist high stresses over arelatively wide linear distance to avoid concentration of stress at anyone linear point such as would produce tearing of the plastic sheetmaterial. It is desirable to design the carton and locks so thatstresses will not produce delamination or crazing in highly orientedmaterial so as to avoid discloration and marring of the surface.

It is an object of the present invention to provide a novel method forcold-folding blanks of synthetic plastic sheet material.

It is also an object to provide such a method which is operable atrelatively high speeds and which is adapted to forming a six-sidedcontainer having a rugged lock for overlying panels.

Another object is to provide a high-speed folding method wherein theblank may be folded into condition to receive the intended contents inone complete revolution of a folding mandrel with the necessary locksand engagements being made during the rotation of the mandrel.

Other objects and advantages will be readily apparent from the followingdetailed specification and the attached drawings wherein:

FIGURE 1 is a perspective view of a container embodying the presentinvention;

FIGURE 2 is a fragmentary perspective view of the bottom end of thecontainer of FIGURE 1;

FIGURE 3 is a fragmentary perspective view to an enlarged scale of alock on the body portion;

FIGURE 4 is a fragmentary perspective view to an enlarged scale of aslip lock on the bottom end of the container;

FIGURE 5 is a sectional view along the line 55 of FIGURE 4;

FIGURE 6 is a plan view to a reduced scale of the blank for thecontainer of FIGURE 1;

FIGURE 7 is a similar view of the blank of FIGURE 6 with the lines ofintended fold indicated in dotted line;

FIGURE 8 is a perspective view showing diagrammatically the first stepin folding the blank of FIGURE 6 into the container of FIGURE 1;

FIGURE 9 is a fragmentary end view showing the blank positioned forfurther folding by a folding mandrel;

FIGURE 10 is a perspective view showing diagrammatically the next stepin the folding sequence;

FIGURE 11 is a similar view showing another step in the foldingsequence;

FIGURE 12 is a similar view showing a further step in the foldingsequence;

FIGURE 13 is a similar view showing the last fold being made in the bodyportion;

FIGURES 14 through 16 are sectional views showing diagrammatically theengagement of the interlock of the present invention; and

FIGURE 17 is a fragmentary perspective view diagrammaticallyillustrating the folding of the top end flaps.

We have now found that the foregoing and related objects can be attainedby a container integrally formed from a blank of synthetic plastic sheetmaterial and having front, rear and side wall panels forming arectangular body and a side flap on a side panel which overlies the rearpanel and which is adapted to be engaged with the rear panel, preferablyby a locking tab thereon engaged in a locking incision in the rearpanel, although other means such as adhesives, heat-sealing or solventsealing or external means may also be employed. Along the bottom edge ofthe wall panels are provided a bottom end wall flap, a pair of dustflaps, and a locking flap which extend perpendicularly thereto and areengaged to provide the bottom closure. The locking flap is located uponthe edge of the one side wall panel and engages with the end wall flapwhich is located upon the other side wall panel, conveniently by alocking tab on one flap and a cooperating incision in the other flap.Along the top edge of the wall panels are provided a pair of dust flapsand an elongated flap which is folded to provide an end flap overlyingthe dust flaps and a tuck or locking flap extending perpendicularlythereto along the surface of the body of the container to provide areleasable closure for the container although a similar locking tab andincised end wall flap may be employed for a strong lock in place of thesimple tuck flap if so desired.

In the method of folding the blank of the present invention into thecontainer, a single mandrel is employed for forming the elongated foldsdefining the various wall panels of the body with a preliminary stepbeing the formation of a transverse fold across the bottom end of theblank to fold and set up the bottom wall flaps. The blank with the endfold is then supported upon a series of pivotally mounted supportmembers having their axes coinciding with the intended lines of fold anda top surface or pad of resiliently deformable material. The mandrel hasits side faces dimensioned to correspond with the intended width of thewall panels and to align the edges with the intended lines of fold. Thesides of the mandrel adjacent the edges are undercut to provide knifeedges along the sides. The mandrel is supported for rolling movementlaterally over the several support members so as to depress the plasticmaterial of the blank into the resiliently deformable material of thepads, which deformation also forces the plastic material about theundercut side edges of the mandrel to effect the desired fold therein.As the mandrel rolls along the blank from pad member to pad member, thedust flaps and locking flaps are engaged with the bottom end wall flap;and, where a locking tab is employed, as the mandrel makes the finalfold for the side flap along the side of the last panel, the locking tabthereon is engaged in the incision of the adjacent wall panel.

Thus, the blank is readily and speedily folded into the container formready to receive the contents. The folds in the top end flaps areconveniently effected by a simple folding blade which is inserted intoposition with its edges aligned with the intended folds in the dustflaps and top flap, and die pads of resiliently deformable material aremoved against the blank and folding blade so as to cause the resilientlydeformable material to flow about the 3 blank and folding blade andforce the plastic material about the edges of the blade and form thefold therein. The fold defining the tuck flap can be made either beforeor after the other folds either by moving a folding blade towards asupporting pad of resiliently deformable material or vice versa.

The lock of the present invention is formed by providing a complexcurvilinear incision in the underlying panel which includes a pair ofopposed and aligned generally S-shaped slits having opposed arcuateportions pointing towards each other at the ends of the slits spacedaway from the free end of the panel and reversely curved arcuateportions with terminal portions extending towards each other at the endthereof adjacent the free end of the panel. A transverse arcuate slitpointing towards the free end of the panel intersects the S-shaped slitsat the opposed arcuate portions at a point spaced from the point oftheir closest proximity towards the free end of the panel and provides apair of hinged flaps between the S-shaped slits. The overlying lockingflap is provided on its outer edge with a projecting locking tab ofgenerally dovetailed configuration having a free end of greater widththan the root portion thereof and of greater width than the spacingbetween the S-shaped slits at the point of closest proximity between theopposed arcuate portions and at the point of greatest separation betweenthe reversely curved portions. The width of the tab tapers to a reduceddimension at the root whereat it is of lesser dimension than the spacingbetween the reversely curved portions of the S-shaped slits at theirpoint of greatest separation. In this manner, the locking tab may bethrust through the incision and engaged behind the underlying panel withthe hinged flap defined by the opposed arcuate portions of the S-shapedslits and the transverse slit resiliently bearing against its top orouter surface of the tab and the hinged flap defined by the reverselycurved portions and transverse slit resiliently bearing against itsinner or bottom surface. The tapered side edges of the tab butt againstthe arcuate sides of the opposed S-shaped slits to limit movementtransversely and are retained from movement in the major direction ofthe slits by width of the free end of the tab which is greater than thewidth between the slits at their point of closest proximity and alsogreater than the width between the reversely curved portions.

Turning now in detail to the attached drawings, FIG- URE 6 illustrates ablank embodying the present invention generally designated by thenumeral 1 which is folded into the container of FIGURES 1 through 5. Theblank 1 is integrally formed of synthetic plastic sheeting which willtake and hold a fold and which is relatively rigid while providingresiliency to resist the normal stresses and impacts to which thecontainer may be subjected during usage. The blank is incised along itsedges at the lines of intended fold to define top and bottom end panels,but the surfaces of the blank are smooth and unscored or otherwiseunbroken.

More particularly, as best seen in FIGURE 7 wherein the dotted linesindicate the intended lines of fold, the body portion of the blankprovides sequentially a rear wall panel 2, side wall panel 6, front wallpanel 8, side wall panel 10 and the side flap 12 which, in theillustrated embodiment, has a pair of locking tabs 14 on its outer egewhich engage in the pair of spaced incisions 4 in the rear wall panel 2adjacent the free end thereof. The cuts in the blank provide a pair ofdust flaps 16 along the bottom edge of the rear and front wall panels 2,8, a locking flap 28 on the side wall panel 10, and a bottom end wallflap 18 upon the side panel 6. The bottom end wall flap 18 has a pair ofarcuate incisions 20 adjacent to the inner end thereof in which engagethe projecting noses 22 on the sides of the dust flaps 16 which overliethe bottom end wall fiap 18. As best seen in FIGURES 4 and 6, the sidesof the dust flaps 16 taper inwardly towards the noses 22 to facilitatepassage of the noses 22 into the arcuate incisions 20 during folding asshown in FIGURE 4 and as will be pointed out more in detail hereinafter.Adjacent its free end, the bottom end wall flap 18 is provided with alocking incision 24 in which engages the locking tab 26 of the lockingfiap 28. Thus, as shown in FIGURE 2, the bottom end wall flap 18 and thedust flaps 16 interengage and are locked in position by the overlyinglocking flap 2% to provide a substantially rigid and high-strengthclosure for the bottom end of the container.

At the opposite or top edge of the body portion in the erected position,cuts in the blank provide dust fiaps 30 on the side wall panels 6, 10and an elongated fiap generally designated by the numeral 32 on the rearwall panel 2. The flap 32 is folded as indicated by the dotted line inFIGURE 7 to provide a top end wall panel portion 34 overlying the dustflaps 30 and a tuck flap portion 36 extending normally thereto along theinner surface of the front wall panel 3, thus enabling facile openingand closing of the container. Due to the inherent resiliency of theplastic sheet, the tuck flap portion 36 is biased against the surface ofthe front wall panel 8, thus enabling facile opening and closing of thecontainer. Due to the inherent resiliency of the plastic sheet, the tuckflap portion 36 is biased against the surface of the front wall panel 8to provide a relatively secure closure.

Turning now in detail to the interlock of the present invention which isbest shown in FIGURE 3 with respect to the lock for the side wall panelsand FIGURES 14 through 16 with respect to the lock for the bottom endwall panel, the underlying panel is provided with a complex curvilinearincision including an S-shaped slit 38 and an inverted S-shaped slit 40spaced therefrom disposed so that the slits have opposed arcuateportions pointing towards each other at the ends spaced away from thefree end of the panel and reversely curved portions with terminalportions extending towards each other at the ends adjacent the free endof the panel. A transverse arcuate slit 42 pointing towards the free endof the panel intersects the S-shaped slit 38, 40 at the opposed arcuateportions but spaced towards the free end of the panel from their pointof closest proximity. In this manner, a pair of hinged flaps 44, 46 areprovided between the S-shaped slits 38, 40.

The overlying panel or flap (numeral 12 in FIGURE 3; numeral 28 inFIGURES 14-16) has a locking tab (numeral 44 in FIGURE 3; numeral 26 inFIGURES 14-16) extending therefrom which is generally of dovetailedconfiguration with its free end being of greater width than its rootportion and also of greater width than the spacing between the S-shapedslits 38, 40 at the point of closest proximity between the opposedarcuate portions and the point of greatest separation between thereversely curved portions. The sides of the locking tab taper inwardlyto the root portion which is of greater width than the spacing betweenthe opposed arcuate portions of the slits at their point of closestproximity but of lesser width than the spacing between the reverselycurved arcuate portions adjacent the free end of the panel at theirpoint of greatest separation.

Because of the inherent resiliency of the synthetic plastic sheetmaterial, the locking tab can be bent and thrust through the slits 38,40 adjacent the free end of the panel so that it overlies the flap 44which resiliently bears against its inner surface and it in turn isoverlain by the flap 46 which resiliently bears upon its outer surface.Since the locking tab, including its root portion, is of greater widththan the spacing between the opposed arcuate portions of the slits 38,40 at their point of closest proximity, movement of the tab in thedirection away from the free end of the underlying panel is limited bythe abutment of its side edges against the edges of the opposed arcuateportions of the slits which decrease in distance of separation to theirpoint of closest proximity. Movement of the tab towards the free end ofthe panel is limited by the bottoming of the tab in the reversely curvedarcuate portions since the free end of the tab is of greater width thanthe distance between the reversely curved portions at their point ofgreatest separation. By proper dimensioning of the tab and incision, thetab 14 can be seated within the incision so that the side edges of itsroot portions are in close proximity to the reversely curved arcuateportions adjacent the free end of the panel to minimize even further thelittle lateral movement which is permitted before the side edges of thetab abut against the sides of the slits. Since the overlying panels areclamped together by the inherent resiliency of the flaps '56, there issubstantially no tendency for external bowing and thus substantiallyparallel external surfaces are provided.

The method of folding the blank into the container is diagrammaticallyillustrated in FIGURES 8 through 17. The first step is illustrated inFIGURE 8 wherein the blank 1 is supported upon a die pad 48 ofresiliently deformable material, such as rubber, along the intersectionof the bottom flaps with the body panels. A rigid folding blade 5dpresses the blank into the rubber-like material of the die pad 43 andcauses the rubber-like material to flow and press the blank about theedge of the folding blade Sil. As pointed out in the aforementionedPalmer United States Patent No. 2,954,725, the blade Sil is preferablyat an acute angle with respect to the surface of the blank 1 so that theflaps will be folded about the edge of the blade to an angle greaterthan 90 degrees, thus overfolding the plastic material to compensate forany inherent relax characteristics therein and provide a permanent bendor fold therein.

As seen in FIGURES 9 and 10, the blank 1 is then supported upon a seriesof pivotally mounted rocker support members 5 56, 58 and as, and theblank l is located thereon with the intended lines of fold in the bodyportion in substantial alignment with the axes of pivotal movement. Anend support 62 and intermediate supports 6d between the several supportmembers are preferably provided. The several rocker supports 54-66, theend support 62 and the intermediate supports 64 are each provivded witha pad 66 0f resiliently deformable or rubber-like material upon whichthe blank 1 is disposed to provide four spaced and independentlypivotable die pad elements.

A folding mandrel 63 is carried by the support arm 7% which extendstherefrom beyond the upper end flaps for rolling movement laterally overthe blank and supports. The mandrel 63 is of generally rectangularconfiguration with its sides dimensioned so that the side edges willalign with the intended lines of fold in the body of the blank and theaxes of the rocker support members during rotation of the mandrel. Asbest seen in FIG- URE 9, the sides of the mandrel 6% are provided withundercut portions '72 adjacent the edges to provide knifelike edges '74.

As best seen in FIGURE 9, the rocker supports 54*, 56, 58, and as arepreferably biased in the at-rest position to a position wherein theupper surface is slightly inclined towards the folding mandrel 63 toensure firm engagement with the mandrel 68 as it rolls thereonto and tolimit or prevent slippage of the blank therebetween. An angle of about 8to 18 degrees has proven satisfactory. By the pivotal mounting of therocker supports, the supports roll with the rotating mandrel to maintainthe blank in contact with the surface thereof. Thi pivotal support hasbeen found to accommodate variations in the relative speed of rotationand speed of lateral movement of the mandrel.

In FIGURE 10, the mandrel 68 has rolled and pressed the plastic sheetmaterial of the blank 1 into the pad 66 of deformable material on therocker support member 54 and the resiliently deformable material thenflows to press the plastic sheet material about the knife edge 74 intothe undercut recesses '72 to overfold the plastic sheet material andprovide a permanent fold. As the mandrel as is making the fold, theresilient material of the pad -56 holds the rear panel 2 against theside of the mandrel 68, and a finger 76 presses against the dust flap 16and thereby the bottom end wall flap 13 to guide the nose portion 22 ofthe dust flap 16 into the arcuate incision As the mandrel 6d continuesto roll, the rocker support memher 54 pivots in the direction of itsrotation to prevent slippage of the blank relative to the mandrel.

In FIGURE 11, the second fold is being made on the rocker support 56 anda finger '78 simultaneously presses against the other dust flap 16 toguide the nose 22 into the arcuate incision 26. In FIGURE 12, the thirdfold is being made upon the rocker support member 53. As the mandrel 6t;continues to roll and the side wall panel portion of the blank restsagainst the bottom of the mandrel 63, the intermediate support 64between the rocker support members 58, so, a finger 82 presses againstthe locking tab at to thrust it inwardly of the locking incision 24 asshown in FIGURES 14 through 16.

As the mandrel 68 rolls over the last rocker support member 6d, the lastfold of the body defining the side flap 12 is made to provide a tubularbody element and, as the mandrel 63 continues to roll, the side flap 12moves into position closely overlying the rear panel 2 for engagementtherewith. In the illustrated embodiment, the fingers thrust the lockingtabs 14 inwardly of the incisions to lock the body panels in assemblyand provide a container body ready to receive the merchandise to beplaced therein.

As shown in FIGURE 17, after the container has been filled, a foldingblade 84- carried by the support arm 36 is inserted over the top edge ofthe front panel 3 into the top of the container with its edges alignedwith the lines of intended fold in the dust flaps 3d and elongated flap32,.

As shown, the upper edge of the front panel 8 is spaced below theintended lines of fold and the cuts defining the several flaps so as tocompensate for the thickness of the folding blade 34 which extendsthereover. Die supports 3b are carried by support arms 92 and spacedabout the side panel Ell, the rear panel 2, and side panel 6 formovement relative thereto and have pads of resiliently deformablematerial on their faces adjacent the container. When the supports 88 arepressed against the container, the rubber-like material flows and formsthe plastic sheet material about the edges of the folding blade 84- tomake the folds therein defining the top flaps.

Either before or after making the above folds, the fold defining thetuck flap 36 can be similarly made by use of a separate folding bladeand die pad of resilient material (not shown).

As can be seen, the folding operation are readily adapted to automaticpackaging machinery and can be conducted at rapid speeds on theproduction lines. In place of the simple tuck flap closure for the upperend wall, a mechanical interlock can also be utilized. In place of thelocking tab and incision interlock for the side flap and underlying wallpanel, adhesive solvent sealing or heat sealing may also be employed orexternal means may ensure the desired closely overlying position thereofin the assembled container.

The synthetic plastic sheet material should be semi-rigid withsufficient flexibility to accommodate tresses and impacts occurringduring normal usage. The material should also have the characteristicsof being foldable and retaining a fold in accordance with theaforementioned Palmer patent. From the standpoint of optimum aestheticqualities and visibility, the plastic sheeting should be clear andrelatively resistant to scratching during normal usage. Although anumber of plastic materials may be satisfactorily employed, biaxiallyoriented polystyrene of about 5 to 15 mils thickness has beenadvantageously employed because of its clarity, high strength andserni-rigidity coupled with sufficient resiliency and flexibility toprovide durable folds and resistance to normal impacts.

As can be readily appreciated, the container of the present invention ishighly attractive and relatively rigid in assembly to provide ahigh-strength package. The mechanical interlock of the present inventionis of high strength and limits relative displacement of overlying panelseven to the point of causing damage to the panels to effectdisengagement. The blank and method enable the erection of the containerspeedily and in simple sequences adapted to automatic packagingequipment in high-speed production lines.

Having thus described the invention, we claim:

1. In the method of forming a container of synthetic plastic sheetmaterial, the steps comprising forming an unscored container blank ofsemi-rigid synthetic plastic sheet material and including a body portionadapted to be cold folded into four wall panels defining a containerbody of rectangular configuration and a side-locking flap along oneouter side thereof, said blank having a locking tab on said one outerside and a cooperating locking incision adjacent the other outer sidethereof for interengagement upon folding of the blank into therectangular body configuration, said blank being incised along one edgeat the lines of intended fold for the wall panels of the body to providea bottom end wall flap, a pair of dust flaps and an end-locking flap andadapted to provide a closure for one end of the container, saidend-locking flap and endwall flap being spaced apart by a dust flap andone of said locking flap and end-wall flap extending from the portion ofthe blank adjacent said locking flap of the body portion, one of saidlocking flap and end wall flap having a locking incision therein and theother of said locking flap and end wall flap having a locking tabthereon engageable in said incision to provide a firm closure, saidblank being incised along the other edge thereof at the lines ofintended fold for the said Wall panels to provide flaps adapted to befolded into a closure for the other end of said body; supporting thesaid blank between a die pad of resiliently deformable material and arigid folding blade with the die pad providing resilient support forsaid blank along the intended fold line for the flaps along said oneedge and defined by the inner end of the incisions therein forming theflaps; causing said blade to press said blank into said die pad alongsaid line of intended fold to cause said deformable material to flow andfold the blank about the blade to establish a permanent fold in saidblank defining the flaps on said edge; supporting said folded blank on adie pad of resiliently deformable material along the intended lines offold defining the several wall panels of the body; and rolling a foldingmandrel of generally rectangular cross section over said blank to causethe side edges thereof to press said blank into the deformable materialalong the intended lines of fold and cause the deformable material toflow and fold the blank about the side edges of the mandrel to establishpermanent folds in the blank and form a rectangular body portionconforming generally to the periphery of said mandrel with a side flapoverlying the adjacent wall panel formed by the other outer side of theblank, said locking tab of the side flap being thrust into said lockingincision of the panel formed by the said other outer side during therotation of the mandrel.

2. The method in accordance with claim 1 wherein said plastic sheetmaterial of the blank is of biaxially oriented polystyrene of 5 to milsthickness.

3. The method in accordance with claim 1 wherein said locking incisionsof the blank are comprised of a pair of opposed generally S-shaped slitsand an arcuate slit extending transversely thereof and intersecting saidS-shaped slits, said S-shaped slits having opposed arcuate portions atthe ends spaced away from the edge of the blank and reversely curvedportions with their termini extending towards each other at the endsadjacent the edge of the blank, said transverse arcuate slitintersecting said opposed arcuate portions at a point spaced towards theedge of the blank from their point of closest proximity and providing apair of hinged flaps between said S-shaped slits and wherein each ofsaid locking tabs is of generally dovetailed configuration with its freeend being of greater width than the spacing between said S-shaped slits,said tabs tapering inwardly to a reduced width at the root portion whichis of greater width than the spacing between the opposed arcuateportions at their point of closest proximity but of lesser width thanthe spacing between the reversely curved arcuate portions of their pointof greatest separation, said tabs being adapted to extend inwardly ofsaid incisions at a point spaced towards the edge of the underlyingpanel from the point of closest proximity between said opposed arcuateportions with the sides of its free end portions being disposed alongthe inner surface of the underlying panels outwardly of said incisionsat said opposed arcuate portions whereby said tabs will overlie thehinged flaps adjacent the edges of the underlying panels and the othersof said hinged flaps will overlie said tabs and said hinged flaps willresiliently bear against the surfaces of said tabs to provide firmengagement.

4. In the method forming a container of synthetic plastic sheetmaterial, the steps comprising forming an unscored container blank ofsemi-rigid synthetic plastic sheet material and including a body portionadapted to be cold-folded into four Wall panels defining a containerbody of rectangular configuration and a body-locking flap along oneouter side thereof adapted to overlie the wall panel provided by theother outer side thereof, said blank having a pair of spaced lockingtabs on said one outer side thereof and a pair of cooperating lockingincisions adjacent the other outer side thereof for interengagement uponfolding of the blank into the rectangular body configuration with thebody-locking fiap overlying the wall panel provided "by the other outerside of the blank, said blank being incised along one edge at the linesof intended fold for the wall panels of the body to provide an end wallflap, a pair of dust flaps and an end-locking flap extending from oneedge of the wall panel portions and adapted to be folded to extendnormally to said wall panel portions and interengage to provide aclosure for one end of the container, said endloeking flap and end wallflap being spaced apart by a dust flap and said locking flap extendingfrom the wall panel portion of the blank adjacent said body-lockingflap, said end wall flap having a locking incision therein adjacent thefree end thereof and said locking flap having a locking tab thereonengageable in said locking incision to provide a firm closure for oneend of the container, said blank being incised along the other edgethereof at lines intended fold for the said wall panels to provide flapsadapted to be folded into a closure for the other end of the container,said locking incisions being each comprised of a pair of opposedgenerally S-shaped slits and a slit extending transversely thereof andintersecting said S-shaped slits, said S-shaped slits having opposedarcuate portions at the ends spaced away from the edge of the blank andreversely curved portions with their termini extending towards eachother at the ends adjacent the edge of the blank, said transverse slitintersecting said opposed arcuate portions at a point spaced towards theedge of the blank from their point of closest proximity and providing apair of hinged flaps between said S- shaped slits, said locking tabseach being of generally dovetailed configuration with its free end beingof greater width than the spacing between said S-shaped slits andtapering inwardly to a reduced width at its root portion which isgreater in width than the spacing between the opposed arcuate portionsat their point of closest proximity but of lesser width than the spacingbetween the reversely curved areuate portions at their point of greatestseparation, said tabs being adapted to extend inwardly of said incisionat a point spaced towards the edge of the underlying panel from thepoint of closest proximity between said opposed arcuate portions withthe sides of its free end portion being disposed along the inner surfaceof the underlying panel outwardly of said incision at said opposedarcuate portions whereby said tabs will overlie the hinged flap adjacentthe outer edge of the underlying panel and the other of said hingedflaps will overlie said tab and said hinged flaps will resiliently bearagainst the surfaces of said tab to provide firm engagement; supportingthe said blank between a die pad of resiliently deformable material anda rigid folding blade with the die pad providing resilient support forsaid blank along the intended fold line for the flaps along said oneedge and defined by the inner end of the incisions forming the flaps;causing said blade to press said blank into said die pad along said lineof intended fold to cause said deformable material to flow and fold theblank about the blade to establish a permanent fold in said blankdefining the fiaps on said one edge; supporting said folded blank on diepads of resiliently deformable material along the intended lines of folddefining the wall panels of the body; and rolling a folding mandrel ofgenerally rectangular cnoss section over said blank to cause the sideedges thereof to press said blank into the deformable material of thedie pads along the intended lines of fold and cause the deformablematerial to fiow and fold the blank about the side edges of the mandrelto establish permanent folds in the blank and form a rectangular bodyportion conforming generally to the periphery of said mandrel with abody-locking flap overlying the adjacent wall panel formed by the saidother outer side of the blank, said locking tabs of the body-lockingflap being thrust into said locking incisions of the panel formed by thesaid other \OHIEI side of the blank during the rotation of the mandrelthereover and said flaps of said one edge being formed into superposedrelationship with the end-locking flap being disposed outwardly of saidend wall flap and dust flaps and the locking tab therein being thrustinto the locking incision in said end wall flap during rotation of themandrel thereover.

5. The method of claim 4 wherein said die pads supporting the foldedblank along the intended lines of fold defining the wall panels of thebody pivot about an axis in substantial alignment with the intendedlines of fold during the notation of the mandrel thereover.

6. In the method of forming a container of synthetic plastic sheetmaterial, the steps comprising forming an unscored container blank ofsemi-rigid synthetic plastic sheet material and including a body portionadapted to be cold-folded into four wall panels defining a containerbody of rectangular configuration and a body-locking flap along oneouter side thereof adapted to overlie the wall panel provided by theother outer side thereof, said blank having a pair of spaced lockingtabs on said one outer side thereof and a pair of cooperating lockingincisions adjacent the other outer side thereof for interengagement uponfolding of the blank into the rectangular body configuration with thebody-locking flap overlying the Wall panel provided by the other outerside of the blank, said blank being incised along one edge at the lineof intended fold for the wall panels of the body to provide an end wallflap, a pair of dust flaps and an endlocking flap extending from oneedge of the wall panel portions and adapted to be folded to extendnormally to said wall panel portions and interengage to provide aclosure for one end of the container, said end-locking flap and end wallflap being spaced apart by a dust flap and said locking flap extendingfrom the wall panel portion of the blank adjacent said body-lockingflap, said end wall flap having a locking incision therein adjacent thefree end thereof and said locking flap having a locking tab thereonengageable in said locking incision to provide a firm closure for oneend of the container, each of said dust flaps having a nose projectingfrom the free end thereof at the sides adjacent the bottom end wall flapand said bottom end wall flap having a pair of spaced arcuate slitsadjacent the inner end thereof into which said noses of the dust flapsare adapted to extend upon folding of the blank, said blank beingincised along the other edge thereof at lines of intended fold for thesaid wall panels to provide flaps adapted to be folded into a closurefor the other end of the container, said locking incisions being eachcomprised of a pair of opposed generally S-shaped slits and a slitextending transversely thereof and intersecting said S-shaped slits,said S-shaped slit having opposed arcuate portions at the ends spacedaway from the edge of the blank and reversely curved portions with theirtermini extending towards each other at the ends adjacent the edge ofthe blank, said transverse slit intersecting said opposed arcuateportions at a point spaced towards the edge of the blank from theirpoint of closest proximity and providing a pair of hinged flaps betweensaid S-shaped slits, said locking tabs each being of generallydovetailed configuration with its free end being of greater width thanthe spacing between said S-shaped slits and tapering inwardly to areduced width at its root portion which is greater in width than thespacing between the opposed arcuate portions at their point of closestproximity but of lesser width than the spacing between the reverselycurved arcuate portions at their point of greatest separation, said tabsbeing adapted to extend inwardly of said incision at a point spacedtowards the edge of the underlying panel from the point of closestproximity between said opposed arcuate portions with the side of itsfree end portion being disposed along the inner surface of theunderlying panel outwardly of said incision at said opposed arcuateportions whereby said tabs will overlie the hinged flap adjacent theouter edge of the underlying pane] and the other of said hinged flapswill resiliently bear against the surfaces of said tab to provide firmengagement; supporting the said blank between a die pad of resilientlydeformable material and a rigid folding blade with the die pad providingresilient support for said blank along the intended fold line for theflaps along said one edge and defined by the inner end of the incisionsforming the flaps; causing said blade to press said blank into said diepad along said line of intended fold to cause said deformable materialto fiow and fold the blank about the blade to establish a permanent foldin said blank defining the flaps on said one edge; supporting saidfolded blank on die pads of resiliently deformable material along theintended lines of fold defining the wall panels of the body; and rollinga folding mandrel of generally rectangular cross section over said blankto cause the side edges thereof to press said blank into the deformablematerial of the die pads along the intended lines of fold and cause thedeformable material to flow and fold the blank about the side edges ofthe mandrel to establish permanent folds in the blank and form arectangular body portion conforming to the periphery of said mandrelwith a body-locking flap overlying the adjacent wall panel formed by thesaid other outer side of the blank, said locking tabs of thebody-locking flap being thrust into said locking incisions of the panelformed by the said other outer side of the blank during the rotation ofthe mandrel over said blank, said folded dust flaps of said one edgebeing directed outwardly of the said end Wall flap and having theirnoses inserted into the arcuate slits in said end wall panel duringrotation of the mandrel over said blank, and said end locking flap onsaid one edge being directed outwardly of said dust flaps and having itslocking tab thrust into said locking incision during rotation of themandrel over said blank.

7. In the method of forming a container of synthetic plastic sheetmaterial, the steps comprising supporting a blank of synthetic plasticsheet material between a die pad of resiliently deformable material anda folding mandrel of generally rectangular cross section and havingundercut portions in its side surfaces adjacent the side edges; androlling said mandrel over said blank to press said blank into theresiliently deformable material and cause the deformable material toflow and fold the blank about the side edges of the mandrel to establishpermanent folds in the blank and form a rectangular body portionconforming generally to the periphery of said mandrel with a flap on oneside of the blank overlying the wall panel formed by the other side ofthe blank.

8. The method in accordance with claim 7 wherein said blank is supportedupon a die pad composed of four separate die pad elements each mountedfor independant pivotal movement about an axis substantially coincidingwith a side edge of the mandrel during rotation thereof over said blankand wherein said die pads pivot with said mandrel as it rotatesthereover.

9. The method in accordance with claim 7 wherein said synthetic plasticsheet material is biaxially oriented polystyrene of about 5-15 mils inthickness.

10. In the method of forming a container of synthetic plastic sheetmaterial, the steps comprising forming an unscored container blank ofsemi-rigid synthetic plastic sheet material and including a body portionadapted to be cold folded into four wall panels defining a containerbody of rectangular configuration and a side flap along one outer sidethereof, said blank being incised along one edge at the lines ofintended fold for the wall panels of the body to provide a bottom endwall flap, a pair of dust flaps and an end-locking flap and adapted toprovide a closure for one end of the container, said end-locking flapand end-wall flap being spaced apart by a dust flap and one of saidlocking flap and end-wall flap extending from the portion of the blankadjacent said locking flap of the body portion, said locking flap andend-wall flaps being adapted to be engaged to provide a firm closure,said blank being incised along the other edge thereof at the lines ofintended fold for the said wall panels to provide fiaps adapted to befolded into a closure for the other eudof said body; supporting the saidblank between a die pad or resiliently deformable material and a rigidfolding blade with the die pad providing resilient support for saidblank along the intended fold line for the flaps along said one edge anddefined by the inner end of the incisions therein forming the flaps;causing said blade to press said blank into said die pad along said lineof intended fold to cause said deformable material to flow and fold theblank about the blade to establish a permanent fold in said blankdefining the fiaps on said edge; supporting said folded blank on a diepad of resiliently deformable material along the intended lines of folddefining the several wall panels of the body; and rolling a foldingmandrel of generally rectangular cross section over said blank to causethe side edges thereof to press said blank into the deformable materialalong the intended lines of fold and cause the deformable material tofiow and fold the blank about the side edges of the mandrel to establishpermanent folds in the blank and form a rectangular body portionconforming generally to the periphery of said mandrel with a side flapextending along the surface of the adjacent wall panel formed by theother outer side of the blank.

11. The method in accordance with claim 10 wherein one of said lockingflap and said end wall flap has a locking incision therein and the otherthereof has a locking tab thereon engageable in said incision to providea firm closure, and wherein said locking tab is inserted into saidlocking incison durng the folding of the rectangular body portion bysaid mandrel.

No references cited.

FRANK E. BAILEY, Primary Examiner.

1. IN THE METHOD OF FORM ING A CONTAINER OF SYTHETIC PLASTIC SHEETMATERIAL, THE STEPS COMPRISING FORMING AN UNSCORED CONTAINER BLANK OFSEMI-RIGID SYNTHETIC PLASTIC SHEET MATERIAL AND INCLUDING A BODY PORTIONADAPTED TO BE COLD FOLDED INTO FOUR WALL PANELS DEFINING A CONTAINERBODY OF RECTANGULAR CONFIGURATION AND SIDE-LOCKING FLAP ALONG ONE OUTERSIDE THEREOF,SAID BLANE HAVING A LOCKING TAB ON SAID ONE OUTER SIDE ANDA COOPERATING LOCKING INCISION ADJACENT THE OTHER OUTER SIDE THEREOF FORINTERENGAGEMENT UPON FOLDING OF THE BLANK INTO THE TECTANGULAR BODYCONFIGURATION, SAID BLANK BEING INCISED ALONG ONE EDGE AT THE LINES OFINTENDED FOLD FOR THE WALL PANELS OF THE BODY TO PROVIDE A BOTTOM ENDWALL FLAP, A PAIR OF DUST FLAPS AND AN END-LOCKING FLAP AND ADAPTED TOPROVIDE A CLOSURE FOR ONE END OF THE CONTAINER, SAID END-LOCKING FLAPAND END WALL FLAP BEING SPACED APART BYA DUST FLAP AND ONE OF SAIDLOCKING FLAP AND END-WALL FLAP EXTENDING FROM THE PORTION OF THE BLANKADJACENT SAID LOCKING FLAP OF THE BODY PORTION, ONE OF SAID LOCKING FLAPAND END WALL FLAP HAVING A LOCKING INCISION THEREIN AND THE OTHER OFSAID LOCKING FLAP AND END WALL FLAP HAVING A LOCKING TAB THEREONENGAGEABLE IN SAID INCISION TO PROVIDE A FIRM CLOSURE, SAID BLANK BEINGINCISED ALONG THE OTHER EDGE THEREOF AT THE LINES OF INTENDED FOLD FORTHE SAID WALL PANELS TO PROVIDE FLAPS ADAPTED TO BE FOLDED INTO ACLOSURE FOR THE OTHER END OF SAID BODY; SUPPORTING THE SAID BLANKBETWEEN A DIE PAD OF RESILIENTLY DEFORMABLE MATERIAL AND A RIGID FOLDINGBLADE WITH THE DIE PAD PROVIDING RESILIENT SUPPORT FOR SAID BLANK ALONGTHE INTENDED FOLD LINE FOR THE FLAPS ALONG SAID ONE EDGE AND DEFINED BYTHE INNER END OF THE INCISIONS THEREIN FORMING THE FLAPS; CAUSING SAIDBLADE TO PRESS SAID BLANK INTO SAID DIE PAD ALONG SAID LINE OF INTENDEDFOLD TO CAUSE SAID DEFORMABLE MATERIAL TO FLOW AND FOLD THE BLANK ABOUTTHE BLADE TO ESTABLISH A PERMANENT FOLD IN SAID BLANK DEFINING THE FLAPSON SAID EDGE; SUPPORTING SAID FOLDED BLANK ON A DIE PAD OF RESILIENTLYDEFORMABLE MATERIAL ALONG THE INTENDED LINES OF FOLD DEFINING THESEVERAL WALL PANELS OF THE BODY; AND ROLLING A FOLDING MANDREL OFGENERALLY RECTANGULAR CROSS SECTION OVER SAID BLANK TO CAUSE THE SIDEEDGES THEREOF TO PRESS SAID BLANK INTO THE DEFORMABLE MATERIAL ALONG THEINTENDED LINES OF FOLD AND CAUSE THE DEFORMABLE MATERIAL TO FLOW ANDFOLD THE BLAND ABOUT THE SIDE EDGES OF THE MANDREL TO ESTABLISHPERMANENT FOLDS IN THE BLANK AND FORM A RECTANGULAR BODY PORTIONCONFORMING GENERALLY TO THE PERIPHERY OF SAID MANDREL WITH A SIDE FLAPOVERLYING THE ADJACENT WALL PANEL FORMED BY THE OTHER OUTER SIDE OF THEBLANK, SAID LOCKING TAP OF THE SIDE FLAP BEING THRUST INTO SAID LOCKINGINCISION OF THE PANEL FORMED BY THE SAID OTHER OUTER SIDE DURING THEROTATION OF THE MANDREL.